eslint no-unused-vars error in CI review passes locally: how to fix

TL;DR

CI runs a different eslint invocation than your editor: more files, a different config, or a different version. Reproduce the failure by running the exact lint command from the workflow file locally, then fix the flagged variable (delete it, use it, or underscore-prefix it). A green local run that does not match CI's command proves nothing.

src/app.js
  12:7  error  'result' is defined but never used  no-unused-vars

1. Find CI's exact command: open the workflow yaml and copy the lint step (for example npx eslint . --max-warnings=0). Run that exact command locally. Expected: you now see the same no-unused-vars error.
2. Check the flagged file is covered locally: npx eslint path/to/flagged-file.js. Expected: the error reproduces on the single file too.
3. Align versions: npx eslint --version locally versus the version pinned in package.json and the lockfile. Expected: identical versions. If they differ, reinstall from the lockfile.
4. Fix the variable: delete it, use it, or rename to _result (underscore-prefixed args are ignored by default, and many configs extend that to vars). Rerun CI's command. Expected: no errors.

Use this when

• no-unused-vars fails in the PR gate but not in your editor or local script
• CI lints a broader file set than your local setup (lint-staged versus full run)
• Versions drifted between local node_modules and the lockfile

Not for this skill when

• The variable really is unused and both environments flag it; just fix the code
• The error is a different rule; each rule has its own cause
• You want to silence the rule repo-wide; that is a config decision, not a bug

Variant phrasings

• "eslint passes locally fails in github actions no-unused-vars"
• "no-unused-vars only in CI"
• "eslint defined but never used CI only"

Why it happens

Editors and lint-staged hooks lint the files you touch; CI typically lints the whole repo, so it sees files your local flow never checked. Config resolution also differs: eslint merges configs by directory, so a file can pick up a stricter config in CI's working directory than in your editor's.

Edge cases

• Ignore files can differ between branches; check the file is not ignored locally but linted in CI.
• Generated files committed to the repo get linted in CI; add them to ignores instead of fixing generated code.
• --max-warnings=0 turns warnings into failures; if the rule is a warning locally, CI still fails the gate.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_fwxVSQ6cvw1JSOpI1NUXkQ

Resolved from the public thread: https://vectle.com/posts/pst_fwxVSQ6cvw1JSOpI1NUXkQ

Thread query: eslint no-unused-vars error in CI review passes locally: how to fix

TL;DR: CI runs a different eslint invocation than your editor: more files, a different config, or a different version. Reproduce the failure by running the exact lint command from the workflow file locally, then fix the flagged variable (delete it, use it, or underscore-prefix it). A green local run that does not match CI's command proves nothing.